1. Field of the Invention
The present invention relates generally to improvements in the field of fiber optics, and particularly to advantageous aspects of systems and methods for improving reproducibility of splice loss reduction in a pre-splice heat treatment.
2. Description of Prior Art
There is a continuing effort in the optical fiber industry to find ways to reduce optical signal loss when a first type of optical fiber is spliced to a second type of optical fiber. Splice loss may arise for a number of different reasons. For example, if the first fiber has a modefield diameter that is significantly larger or smaller than the modefield diameter of the second fiber, splicing the two fibers together results in a modefield diameter mismatch at the splice point that results in splice loss.
One approach that has been developed to reduce splice loss resulting from modefield diameter mismatch is to use a thermal treatment to cause a diffusion of the dopants in the narrower modefield fiber in the region of the splice. This dopant diffusion causes an expansion of the fiber modefield in the splice region, thereby reducing modefield diameter mismatch. Thermal treatments are described, for example, in Krause, John T. et al., xe2x80x9cSplice Loss of Single-Mode Fiber as Related to Fusion Time, Temperature, and Index Profile Alteration,xe2x80x9d Journal of Lightwave Technology, vol. LT-4, No. 7, 1986, pp.837-40; Tam, H. Y., xe2x80x9cSimple Fusion Splicing Technique for Reducing Splicing Loss between Standard Singlemode Fibres and Erbium-Doped Fibre,xe2x80x9d Electronics Letters, vol. 27, No. 17, 1991, pp. 1597-99; and Ando, Yasuhiro, xe2x80x9cLow-Loss Optical Connector between Dissimilar Single-Mode Fibers Using Local Core Expansion Technique by Thermal Diffusion,xe2x80x9d IEEE Photonics Technology Letters, vol. 4, No. 8, 1992, pp. 1028-31.
Recently, efforts have been made to develop a thermal treatment that is applied prior to splicing. In one such treatment, the lead end of a fiber having a narrower modefield diameter is loaded into a heat treatment station to cause an expansion of the modefield in preparation for splicing to a fiber having a larger modefield diameter. However, it has proven difficult to achieve consistent results using a pre-splice heat treatment technique.
An aspect of the invention provides a heat treatment station for applying a pre-splice heat treatment to a lead end of a first optical fiber having a first modefield diameter. The heat treatment station comprises a base, and a fiber clamp for holding the first optical fiber such that a length of the lead end of the first optical fiber is positioned over a heat source mounted to the base. The heat source causes a controlled expansion of the first fiber modefield at the first fiber lead end to form an internal bridge. The heat treatment station further includes length adjustment means for adjusting the length of the first fiber lead end positioned over the heat source.
Additional features and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings.